Riedel's invasive fibrous thyroiditis is a rare disorder of unknown origin with progressive extension and invasion of adjacent structures. Clinically it is impossible to distinguish between Riedel's/thyroiditis and other diseases as undifferentiated carcinoma, Hashimoto's disease etc... The patients often have dyspnea, dysphagia, paralysis of the vocal cord; fine needle puncture-aspiration and biopsy themselves may be insufficient, Surgical treatment depends on the stage of the disease, when both lobes are involved generous wedge resection of the isthmus may be the treatment of choice to relieve tracheal compression; in earlier stages radical operation are considered. Corticosteroid treatment in Riedel's thyroiditis, as multifocal disease has been successfully used. Other drugs with antifibrosing actions have also utilised in small groups of patients with encouraging results.